The Neurokernel project aims to build an open software platform that can scalably leverage the power of multiple GPUs to emulate the entire fly brain. A key feature of the platform is its support for integrating models of LPUs into models of entire functional subsystems. Neurokernel defines a mandatory module interface for the communication of neuron state data between LPU model implementations. Connectivity patterns between any two LPUs are expressed independently both of other inter-LPU connectivity patterns and the internal connectivity of the LPUs themselves. Enforced LPU interoperability and the partitioning of the fly connectome into connections responsible for distributing data between processing modules and connections that are part of those modules enables individual LPU models or connectivity patterns to be improved or replaced without modification of other parts of a brain emulation. This design facilitates the collaborative development of whole-brain emulations by enabling..